Industrial labeling is one of the methods used for the identification marking of components on vehicles, on machinery, and on electrical and electronic devices, examples being model-identification plates, labels for process control, and guarantee badges and test badges.
Increasing importance is being attached to identification marking by means of laser labels or printed or coated metal plates, specifically in the automotive industry, in particular for high-quality markings. This method is used to place information and advice, such as tire pressure or fuel type, on a very wide variety of components in the automobile for its subsequent user. A laser label may also be used to convey important production data within upstream stages of manufacture.
For this use, the label may be inscribed with a bar code. A suitable reading device gives an assembly team the opportunity of using the bar code for read-off of information concerning model, color, and special equipment, directly on the manufacturing line.
Labels are used on the vehicle not only for this standard information but also for the placing of sensitive security data, such as chassis number and identification numbers. In the event of theft or an accident, this information is very important for tracing of a vehicle and of stages in manufacture.
The label material used therefore has to be highly counterfeit-proof, in order to prevent any attempt at manipulation. It has to be impossible to remove the label intact from the base to which it adheres.
Additional security is achieved by using highly breakable material in combination with high adhesive strengths. The adhesive strength of the material on the adhesion base is very significant. It is a decisive factor for resistance to any attempt at manipulation by removal.
Besides the standard material, there are modified labels intended to eliminate any possibility of imitating the material by using other safety features, such as embossments, holograms, or a lasting UV impression (footprint).
There are widely used high-performance controllable lasers for introducing markings, such as inscriptions, codings, and the like, using a burning process. Some of the requirements placed upon the material to receive the inscription, or used for the inscription process, are:    It has to be capable of rapid inscription.    A high degree of spatial resolution capability has to be achieved.    It has to be very simple to use.    The decomposition products have to be non-corrosive.
For particular cases moreover, additional properties are demanded:    The markings produced by applying the laser have to have sufficient contrast to be capable of being read without error even under unfavorable conditions and over large distances.    Heat resistance has to be high, for example extending above 200° C.    Good resistance to weathering, water, and solvents is desirable.
Complete separation of labels from the substrate is possible using sharp, flat blades. The bond between adhesive mass and substrate exhibits particular weaknesses on plastics substrates, such as polyethylene or polypropylene.
Despite increased adhesive strength on metallic or coated substrates, it is also possible here to remove part of the labels without irreversible damage, by using specific tools. A specific tool with a blade can be passed under the label at a shallow angle. Careful cutting movements can lift an edge, producing what is known as a grab site. This method creates a point of attack, which facilitates release.
This means that labels have a fundamental disadvantage.
If printing, rather than a laser label, is used to apply the inscriptions to the component, third parties can easily remove the inscription by washing or scratching. Simple rubbing of the inscribed article on a second article, for example a packing, is also often sufficient to reduce the clarity of the individual letters or numerals.
It is an object of the invention to provide a multilayer laser-transfer film which permits rapid and precise inscription of any desired component, and which meets the abovementioned demand for improved security against counterfeiting, and which cannot be removed intact, even with the aid of a cutter, and which besides this in particular also has high contrast, high capability for resolution, high heat resistance, and good ease of use.